Tekstilec 2015, letn. 58(1), 23−32 Corresponding author/Korespondenčna avtorica:
Assis. Prof. D.Sc. Dunja Šajn Gorjanc
Dunja Šajn Gorjanc1, Neža Sukič1 and Veronika Vrhunc2
1University of Ljubljana, Faculty of Natural Sciences and Engineering, Department of Textiles, Snežniška ulica 5, SI-1000 Ljubljana
2Predilnica Litija, Kidričeva 1, SI-1270 Litija
The Infl uence of Modacrylic and Metal Protective Fibres in the Mixture on the Mechanical Properties of Ring Spun Yarns for Protective Textiles
Vpliv dodanih vlaken MAC in MTF v mešanici na mehanske lastnosti prstanske preje za varovalne tekstilije
Original Scientifi c Article/Izvirni znanstveni članek
Received/Prispelo 01-2015 • Accepted/Sprejeto 02-2015
Abstract
The research is focused on the infl uence of the fi re resistant modacrylic (MAC) fi bres in the ring-spun yarn mixture with cotton (CO) fi bres and of the conductive metal fi bres (MTF) in the ring-spun yarn mix- ture with polyester (PES) fi bres on the mechanical properties in the region of lower loads. Analysed yarns are intended for the protective clothing production (fi re resistant and electrically conductive clothing).
The viscoelastic behavior of yarns in the fi eld of lower loads under the specifi c stress/extension curve which amounts to 5 cN/tex, reaching the weight of 85 g. The results of the research show that the incor- poration of MAC fi bres in the yarn from the mixture of 55% MAC/45% CO fi bres increases the region of elastic deformations (the stress and extension in the yield point), on the other side the MAC fi bres in the yarn mixture decrease the elasticity modulus level. The incorporation of MTF (stainless stell) fi bres in the yarn mixture consisting of 75% PES/25% MTF decreases the region of elastic deformations (about 10%), however the region of elastic deformations lies very close to the chosen stress value under the specifi c stress/extension curve – 5 cN/tex or 85 g.
Keywords: modacrylic fi bres, metal fi bres, ring-spun yarn, mechanical properties, viscoelastic properties
Izvleček
Raziskava je usmerjena na vpliv ognjevarnih modakrilnih vlaken v prstanski preji iz mešanice modakrilnih in bom- bažnih vlaken in elektroprevodnih kovinskih vlaken v prstanski preji iz mešanice poliestrskih in kovinskih vlaken na mehanske lastnosti v območju manjših (uporabnih) obremenitev. Analizirane preje so namenjene za izdelavo za- ščitnih oblačil (ognjevarnih in elektroprevodnih), tako se raziskava osredinja na viskoelastično območje manjših obremenitev na krivulji napetost/raztezek, tj. pri napetosti 5 cN/tex, kar pomeni obremenitev mase 85 g. Raziska- va je pokazala, da ognjevarna modakrilna vlakna (MAC) v mešanici iz 55 % modakrilnih 45 % bombažnih vlaken vplivajo na povečanje elastičnega območja (napetost in raztezek v meji polzišča), na drugi strani pa vplivajo na znižanje modula elastičnosti prstanske preje. Vsebnost MTF (iz nerjavnega jekla) vlaken v mešanici iz 75 % PES in 25 % MTF vlaken vpliva na zmanjšanje elastičnega območja za okrog 10 %, na drugi strani pa se vrednosti elastič- nega območja gibljejo v mejah območja manjših (uporabnih) obremenitev na krivulji specifi čna napetost/razte- zek, ki znaša 5 cN/tex oziroma 85 g.
Ključne besede: modakrilna vlakna, kovinska vlakna, prstanska preja, mehanske lstnosti, viskoelastične lastnosti
1 Introduction
Th e protection becomes nowadays very important taking into account the industrial developments and the strong need to increase the workwear clothing production, especially in the fi eld of protective clothing. Th e protective textiles have extraordinary importance for the European textile and clothing industries as well as the end users. Protective tex- tiles show high-tech character and are used mainly in the industrial segments. Th e expected average in- crease in Europe in the fi eld of protective textiles production amounts to around 4% [1–3].
Novel developments with complex protection re- quirements are, apart from the protection against electromagnetic radiation, also directed to the pro- tective clothing for electricians working on ener- gized plants with the risk of exposure to very high arcing fl ames. Th e facts presented above have en- couraged the direction of the research in regard to the mechanical behavior of the ring-spun yarn from fl ame resistant and electrically conductive yarn mixtures. Certain authors dealt with the fl ame retardant properties of yarns and fabrics. In recent years, many researchers are interested also in elec- trical and conductive properties of fi bres and fab- rics intended for protective clothing [4–7].
Approximately 90% of global fi ber consumption is processed into yarns, with 57% of the entire pro- duction consisting of yarns from chemical fi bres.
About 8% of the yarn production belongs to the or- ganic fi bres intended for protective clothing, while inorganic fi bres present around 1% of yarn produc- tion intended for protective clothing [8].
Th e number of natural disasters such as fl oodings, landslides and fi res are unfortunately increasing in the last few years. With the increasing of disasters, the need of functional textiles, i. e. the protective clothing for fi refi ghters, rescuers, civil protection, police is also increasing. Th at is the main reason for choosing the research which deals with so–called protective ring-spun yarn loading behavior.
A growing segment of the industrial textiles industry has therefore been involved in a number of new de- velopments in fi bres, fabrics and protective clothing.
For heat and fl ame protection, requirements range from clothing for situations in which the wearers may be subjected to occasional exposure to a moder- ate level of radiant heat as part of their normal work- ing day, to clothing for prolonged protection, where
the wearer is subject to several factors such as radi- ant and convective heat, to direct fl ame, for example the fi refi ghter’s suit.
Th e eff ect of heat on a textile material can produce physical as well as chemical change. In thermoplastic fi bres, the physical changes occur at the glass (Tg), and melting temperature (Tm), while the chemical changes take place at pyrolysis temperatures (Tp) at which thermal degradation occurs. Textile combus- tion is a complex process that involves heating, de- composition leading to gasifi cation (fuel generation), ignition and fl ame propagation. Fibres with LOI (lim- iting oxygen index) greater than 25% are fl ame retard- ant. For protective clothing, however, there are addi- tional requirements, such as protection against heat by providing insulation, as well as high dimensional stability of the fabrics, so that, upon exposure to the heat fl uxes that are expected during the course of the wearer’s work, they will neither shrink nor melt [1, 2].
Th e fi bres could be classifi ed into two categories:
Inherently fl ame–retardant fi bres, such as ara- –
mid, modacrylic, polybenzimidazole (PBI), Pan- ox (oxidised acrylic) or semicarbon, phenolic, as- bestos, ceramic etc.
chemically modifi ed fi bres and fabrics, for exam- –
ple, fl ame retardant cotton, wool, viscose and synthetic fi bres.
Electromagnetic radiation has become the fourth most serious source of public pollution in addition to noise, water and air. It is claimed that the electro- magnetic waves aff ect human health and the per- formance of electrical and electronic devices.
Textile materials made with conductive fi bres and yarns can shield the large part of the electromagnetic waves and protect health of the humans and animals.
Conventional textile fabrics are poor electrical con- ductors. Conducting yarns are used to produce fab- rics for electromagnetic shielding and electrostatic charge dissipation. Such yarns and fabrics are in- creasingly used in applications where fl exibility and conformability are important. Demand for these products has increased rapidly.
Conductive yarns are produced from metal fi bres which have high electrical conductivity, such as stainless steel and copper. Th ey are produced by mixing metal fi bres with chemical fi bres, cotton and viscose fi bres; these increase the electrical conductivity of the fabric, thus eliminating elec- trostatic charges and preventing static loading on the fabric [1–3].
Modacrylic fi bres
Modacrylic fi bres are chemical fi bres which are com- posed of less than 85% but at least 35% by weight of acrylonitrile units and have excellent chemical, sun light and fl ame resistance. Th e modacrylic fi bre melts at around 180–185 °C and exhibits a high range of moisture, around 3.0–3.5%. Temperatures exceeding 150 °C will cause modacrylic fi bre to turn yellow, nevertheless, the modacrylic fi bre has a very good fl ame resistance and good weathering resist- ance. Th e specifi c stress of modacrylic fi bres ranges from 15.9–22.1 cN/tex with 35–40% elongation.
Modacrylic fi bres have high value of elastic recovery (88% at 4% deformation), while their specifi c gravity is 1.37 g/cm3 [10–13].
Metal fi bres
Metal fi bres are fi bres produced from metals, which may be used alone or in combination with other substances. Metal fi bres are produced mainly from aluminum, stainless steel and nickel. Th eir melting point stands at approximately 1426 °C.
Th eir specifi c breaking stress stands at around 22.3 cN/tex, with breaking elongation lower than 1% and they are chemical and thermal resistant.
Th ey are also excellent electrical conductors, rather than stainless steel which is poor conductor, and may be used for resistance heating.
Metal fi bres have higher melting point and are more heat resistant than ordinary fi bres.
In addition, they are fl ame resistant and are used mainly for protective fabrics, carpets, upholstery, work clothing and protective clothing [10–17].
Th e research focuses on the infl uence of the fi re re- sistant modacrylic (MAC) fi bres in the mixture of 55% MAC/45% CO (MAC/CO) fi bres and the con- ductive metal fi bres (MTF) in the mixture of 75%
PES/25% MTF (PES/MTF) fi bres on the mechanical and viscoelastic properties of the ring-spun yarn.
Since the yarns analysed are intended for the pro- tective clothing production, the research focuses on the mechanical behavior of the yarns analysed. Th e research focuses on the fi eld of lower loads under the specifi c stress/extension curve which amounts to 5 cN/tex, wherein the stress presents the weight of around 85 g.
With that purpose the two-plied fi re resistant ring- spun yarn from 100% cotton fi bres (100% CO fi - bres) and the mixture of modacrylic and cotton
two-plied yarn in the percentage ratio of 55%/45%
were analysed in the fi rst part. Furthermore, the re- search focuses on the ring-spun yarn from the 100%
PES fi bres and the electrically conductive yarn from mixture of PES and metal fi bres with the ratio of 75%/25%. In the experimental part the mechanical properties (specifi c stress and extension) were ana- lysed and yarn quality (unevenness) such as yarn imperfections (the mass irregularity CVm, thin and thick areas/1,000 m, neps and yarn hairiness). Th e yarn quality was measured on the Uster Tester, while the mechanical properties of analysed yarns were measured on Statimat Tester. Th e viscoelastic properties (elasticity modulus, the yield point) were calculated from the specifi c stress/extension curve using DINARA®soft ware [9].
2 Materials and methods
In the research, two-plied ring-spun yarn from 100% cotton fi bres and the mixture of modacrylic and cotton fi bres in the ratio of 55% modacrylic fi - bres and 45% cotton fi bres were analysed in the fi rst part (short MAC/CO). While in the second part, the research concentrates on the single ring- spun yarn from the 100% PES fi bres and the yarn from mixture of PES and metal fi bres, with per- centage ratio of 75% PES/25% MTF (short PES/
MTF) fi bres.
Th e yarns analysed were produced in Predilnica Liti- ja from short staple fi bres. Th e fi neness of the sin- gle- and two-plied yarns amounts to 16.67 tex.
Th e two-plied yarn from 100% cotton fi bres and the mixture of modacrylic and cotton fi bres in the ratio of 55% modacrylic fi bres and 45% cotton fi bres is wound, doubled and twisted with 720 and 660 twist per meter in the S-direction (counterclockwise di- rection).
Th e yarn quality and irregularity, yarn imperfec- tions (the mass irregularity CVm in percents, the number of thin and thick areas/1000 m, the number of neps) and yarn hairiness were meas- ured on the Uster Tester, while the mechanical properties (stress and extension) were measured on Statimat tester.
On the Uster Tester the yarn is passed through the electric fi eld of a measuring capacitor. Mass varia- tion of the yarn causes the disturbance of the elec- tric fi eld which is converted into electric signal.
Th e capacitive sensor of Uster Tester is not able to measure the irregularity of special yarns containing electrically conductive material such a metallic fi - bres, etc.
Th e viscoelastic properties such as elasticity modulus and the yield point were calculated using DINARA®
soft ware [9].
Th e scanning electron microscope (SEM) view of analysed ring-spun yarns from the mixture of MAC/
CO and the mixture of PES/MTF fi bres is presented in the Figure 1.
Table 1 presents the basic properties of raw material (fi bres), while Table 2 presents the basic properties of yarns. Th e irregularity (quality) of yarn is meas- ured on the Uster Tester (Table 3).
Table 1: Th e basic properties of fi bres
Type of fi bre Diameter (µm)
Fineness (dtex)
Length (mm)
Specifi c breaking stress (cN/tex)
Breaking extension
(%)
LOI index
(%)
Stainless steel 8.4 2.7 60 22.3 <1 100
Modacrylic 13.7 1.7 38 24.8 33.2 33–34
Cotton 15.6 1.7 34 43.9 10 18–20
Polyester 12.6 1.5 38 60 18 20–22
a b
Figure 1: Th e scanning electron microscope view (cross-sectional) of the ring-spun yarns from the mixture of MAC/CO (a) and the mixture of PES/MTF fi bres (b)
Table 2: Th e basic properties of yarn's samples
Sample Fineness (tex)
Yarn type
Turns per meter
Twist direction
Scanning electron microscope view at magnifi cation
× 120 × 270
× 350 CO
100% 16.67
Two- plied ring- spun
660
S MAC/
CO 16.67 720
PES
100% 16.67
Single ring- spun
770
PES/
MTF 16.67 930
Table 3: Th e mechanical and physical properties of analysed ring-spun yarn
Sample
Raw material Specifi c
breaking stress [cN/tex]
CV of spec.
breaking stress
[%]
Breaking extension
[%]
CV of breaking extension
[%]
Th e mass irregularity
CVm [%]
Th in places/
1000m
Th ick places/
1000m Neps/
1000m
Hairiness/
1000m
CO
100% 23.0 4.0 5.9 7.2 8.8 0 1 2 7.3
MAC
100 % 15.8 6.3 18,7 5.7 9.7 0 0 0 7.8
MAC/CO
55%/45% 13.3 5.8 5.9 9.8 9.8 2 17 29 6.4
PES
100% 34.5 9.7 11.4 8.6 11.8 2 5 14 5.8
PES/MTF 21.8 11.6 12.6 10.3 – – – – –
* Th e mass irregularity, thin places, thick places, neps and hairiness of analysed ring-spun yarn were determined on the Uster Tester (capacitive sensor method) only for non-conductive yarns such are CO, MAC, MAC/CO and PES yarn.
3 Results and discussion
3.1 The results of specifi c breaking stress and extension
Th e results of specifi c breaking stress and extension of analysed fi bres (MAC, CO, PES and MTF) and yarns (MAC/CO, 100% MAC, 100% CO, PES/MTF and 100% PES yarn) are listed in Table 4.
Table 4: Th e results of specifi c breaking stress and bre- aking extension analysed fi bres and yarns
Type of fi bres/yarn
Property Specifi c breaking
stress [cN/tex]
Breaking extension
[%]
Fibres
MAC 24.8 33.2
CO 43.9 10.0
PES 60.0 18.0
MTF 22.3 1.0
Yarns
MAC/
CO 13.3 5.8
100%
MAC 15.8 18.7
100%
CO 23.0 5.9
PES/
MTF 21.8 12.6
100%
PES 34.5 11.4
Th e analysis of specifi c breaking stress (Table 4) of the yarn from the mixture of MAC/CO fi bres has the lo- west value which amounts to 13.3 cN/tex. Th e specifi c breaking stresses of the 100% MAC and the 100% cot- ton yarns are higher (15.8 cN/tex and 23.0 cN/tex).
Th e yarn from the mixture of MAC/CO fi bres has the lowest specifi c breaking stress (13.3 cN/tex) mainly due to the very high diff erence between the specifi c breaking stresses of cotton fi bres (43.9 cN/
tex) and modacrylic fi bres (24.8 cN/tex). Th at re- sults in the specifi c breaking stress level decrease of the MAC/CO yarn, from 23.0 cN/tex (100% cotton yarn) and 15.8 cN/tex (100% MAC yarn) to 13.3 cN/
tex (MAC/CO yarn).
Th e MAC/CO yarn has the breaking extension of 5.8% and similar values are measured with the 100%
CO yarn, while the breaking extension is the high- est with the 100% MAC yarn (18.7%).
Since the fi re protection of the MAC/CO yarn is dominant, MAC fi bres exert the LOI index between 33–34% (the limit of fl ame resistant fi bres of LOI index is 25%) and ensure fi re and heat resistance of the protective clothing produced from that yarn.
Th e specifi c breaking stress of MAC/CO yarn is only about 2% lower than with 100% MAC yarn, but the incorporation of cotton fi bres in the yarn (45% of cotton fi bres in the mixture) is very impor- tant from the point of view of comfort properties (water vapor permeability, air permeability, thermal conduction, etc.) of the yarn intended for the pro- tective clothing.
On the other hand, the results of the mechanical and physical properties of yarn (coeffi cient of the variation of mass, thick and thin areas/1000 m, neps, hairiness) which are listed in Table 3, show that the variation in mass per unit length along the yarn (CVm) is similar and amounts to 9.7% (100%
MAC yarn) and 9.8% (MAC/CO yarn). Th e number of thick and thin areas increases from zero (100%
MAC yarn) and one (100% cotton yarn) to 17 (thick areas/1,000 m) and 29 (neps/1,000 m) of MAC/CO yarn, meaning the yarn from the mixture is non- uniform. Th e irregularity of yarn has a profound in- fl uence on the appearance of yarn and fabric. In contrast, the yarn from the mixture of MAC/CO fi - bres is less hairy (hairiness of 100% MAC yarn is 7.8, while the hairiness of the MAC/CO yarn is 6.4).
Th e main reason of low hairiness lies in the diff er- ent lengths of the MAC fi bres (38 mm) and cotton fi bres (34 mm). Th e percentage of longer MAC fi - bres in the yarn mixture is higher (55%) and pre- vents the transport of shorter cotton fi bres from the inner to the upper (sheath) side of the yarn. On the other hand, lower hairiness of the MAC/CO yarn aff ects the higher abrasion resistance and better ap- pearance of the yarn.
Th e second part of the research is directed to the mechanical properties of protective single PES/
MTF yarn (Table 4) with MTFs which are fi re re- sistant, heat resistant and have high conductivity.
Th e results of the specifi c breaking stress show that the PES/MTF yarn has lower specifi c breaking stress (21.8 cN/tex) than the 100% PES yarn (34.5 cN/tex).
Th e metal fi bres (stainless steel) are coarser (2.7 dtex), longer (60 mm) and thinner (7 µm) than the PES fi bres (fi neness 1.5 dtex, length 38 mm and
diameter 12.6 µm). Metal fi bres have also lower specifi c breaking stress (22.3 cN/tex) in comparison with the specifi c breaking stress of the PES fi bres (60 cN/tex), see Table 1. Consequently, the specifi c breaking stress of the PES/MTF yarn is lower.
Th e results of the yarn quality (coeffi cient of the variation of mass, thick and thin areas/1000 m, neps, hairiness) are measured with the 100% PES yarn (Table 3). Th e results of the yarn quality show that the variation in mass per unit length along the yarn (CVm) amounts to 11.8 and is higher than with the 100% MAC yarn, 100% cotton yarn and MAC/
CO yarn, however the number of thick and thin areas/1000 m and hairiness are lower than with the MAC/CO yarn.
3.2 The results of mechanical behavior of yarns with loading
Th e results of specifi c breaking stress and extension curve of fi bres and yarns from the 100% cotton, the 100% MAC and MAC/CO yarns are shown in Fig- ure 2. Figure 3 shows the specifi c stress/extension curve of the MAC/CO yarn with the 1st, 2nd and 3rd derivatives of the specifi c stress/extension curve.
Th e results of the specifi c breaking stress and exten- sion curve of fi bres and yarns from the 100% PES and the PES/MTF yarn are fi gured in Figure 4. Fig- ure 5 presents the specifi c stress/extension curve of the PES/MTF yarn with the 1st, 2nd and 3rd deriva- tives of the specifi c stress/extension curve.
30 25
20
15
10
5
0
0 2,5 5 7,5 10 12,5 15 17,5 20 22,5 Extension,ε [%]
Specifi c stress,σ [cN/tex]
CO MAC MAC/CO
Figure 2: Th e specifi c stress/extension curve of the 100% CO, 100% MAC and MAC/CO yarn
Th e MAC/CO yarn demonstrates the lowest specifi c breaking stress (13.3 cN/tex) and breaking exten- sion (5.8%). Th e reason lies in the high diff erence between the specifi c breaking stresses and breaking extensions of the 100% CO and the 100% MAC yarn (see Figure 2). In other words, the specifi c breaking stress decreases from 23.0 cN/tex (100%
CO yarn) and 15.8 cN/tex (100% MAC yarn) to 13.3 cN/tex (MAC/CO yarn) (see Figure 2).
Th e straight-shaped MAC/CO yarn specifi c stress/
extension curve represents the yarn with high mod- ulus. Th e MAC/CO yarn has a high resistance to loading in comparison with the 100% MAC yarn.
Th e high resistance of the MAC/CO yarn to loading refl ects in the lower breaking extension. Th e 100%
cotton yarn proves lower breaking extension, while the 100% MAC yarn, which has the highest breaking extension, consequently proves the lowest modulus.
9 7 5 3 1 –1
0 1 2 3 4 5
Extension,ε [%]
Specifi c stress,σ [cN/tex]
MAC/CO Y1 Y2 Y3
Figure 3: Th e specifi c stress/extension curve of MAC/
CO yarn with the 1st (Y1), 2nd (Y2) and 3rd (Y3) de- rivatives
Th e fi rst derivative of the specifi c stress/extension curve of MAC/CO yarn shows lower value of elas- ticity modulus (3.9 cN/tex) than 100% cotton yarn (4.3 cN/tex) (see Figure 3). Th e resistance of yarn on loading in the elastic region – the fi eld of elastic de- formations of the MAC /CO yarn – is about 10%
lower. Th e fi rst deformations in the yarn cause the moving of the fi bres in the sheath. Th at deformations are completely recoverable until they reach the yield point, which presents the limit of elastic region. Th e yield point is calculated from the 2nd and the 3rd de- rivative of the specifi c stress/extension curve in the point where the 2nd derivative is minimal or maxi- mal and 3rd derivative is zero. Th e specifi c stress in
the yield point of the MAC/CO yarn is 7.83 cN/
tex, while the extension in the yield point amounts to 2.1%. On the other hand, the specifi c stress in the yield point of the 100% cotton yarn is 5.42 cN/
tex, while the extension in the yield point amounts to 1.4%.
Th e results of viscoelastic parameters of the MAC/
CO yarn in comparison with results of 100% cotton yarn show that the incorporation of MAC fi bres in the yarn mixture decreases the elasticity modulus of the MAC/CO yarn by about 10%. On the other hand, the incorporation of MAC fi bres increases the yield point level by about 45%, consequently also increasing the fi eld of elastic deformations. Th e spe- cifi c stress in the yield point of the MAC/CO yarn is 7.83 cN/tex, thus being higher than the so-called stress value of 5 cN/tex (85 g), which was selected by this research.
40 35 30 25 20 15 10 5 0
0 2,5 5 7,5 10 12,5 15
Extension,ε [%]
Specifi c stress,σ [cN/tex]
PES PES/MTF
Figure 4: Th e specifi c stress/extension curve of the 100% PES and PES/MTF yarn
Th e PES/MTF yarn has lower modulus and off ers lower resistance to loading than the 100% PES yarn (see Figure 4). Th e reason lies in the specifi c break- ing stress level which is the consequence of the type of raw material and is lower with the PES/MTF yarn (21.8 cN/tex) than with the 100% PES yarn (34.5 cN/
tex). Th e metal fi bres (stainless steel) are coarser (2.7 dtex) and longer (60 mm) than the PES fi bres (fi neness 1.5 dtex and length 38 mm). On the other hand, the MTFs are also thinner and have lower breaking extension (only 1%) than PES fi bres (18%) – see Table 2. Th e MTFs in the PES/MTF yarn break fi rst (they have the lowest breaking extension, 1%) and infl uence the specifi c breaking stress level de- crease of the PES/MTF yarn. Consequently, the PES/MTF yarn has higher breaking extension than
the 100% PES yarn. Th e PES/MTF yarn shows low- er elasticity modulus in comparison with the 100%
PES yarn.
22 19 16 13 7 10 4 1 –5 –2
–11 –8 –14
0 1 2 3 4 5
Extension,ε [%]
Specifi c stress,σ [cN/tex]
PES/MTF Y1 Y2 Y3
Figure 5: Th e specifi c stress/extension curve of the PES/MTF yarn with the 1st (Y1), 2nd (Y2) and 3rd (Y3) derivatives
Th e fi rst derivative of the specifi c stress/extension curve of the PES/MTF yarn (see Figure 5) shows higher value of elasticity modulus (8.67 cN/tex) than the MAC/CO yarn (3.9 cN/tex). Th is would suggest that the PES/MTF yarn ensures higher re- sistance to loading in the elastic region – in the fi eld of elastic deformations (see Figure 5). Th e elasticity modulus of the 100% PES yarn is even higher – 9.64 cN/tex, which is about 10% higher than the elasticity modulus of the PES/MTF yarn. Th e spe- cifi c stress in the yield point of the PES/MTF yarn is 4.33 cN/tex, while the extension in the yield point amounts to 1.5%. Th e specifi c stress and extension in the yield point of the 100% PES yarn amounts to 4.81 cN/tex and 1.5%. Th e both yield point levels are a little bit lower than 5 cN/tex (80 g) which rep- resents the amount chosen as the limit of elastic ex- tension by this research.
Th e results of the viscoelastic parameters (the elas- ticity modulus and the yield point) show that the elasticity modulus of the PES/MTF yarn is about 10% lower than with the 100% PES yarn. On the other hand, the limit of elastic region (the specifi c stress and extension in the yield point) for the PES/MTF yarn is about 10% lower than with the 100% PES yarn. Th e MTFs prove very low break- ing extension (1%) and only slight infl uence on the yield point decrease. Under the yield point, which
presents the numerical limit of elastic deforma- tions, the fi rst movements of fi bres in the sheath appear. Above the yield point, the fi rst movements of the fi bres in the yarn core appear and conse- quently also the viscoelastic deformation (time-de- pendent deformations). Th e specifi c stress/exten- sion curve changes its shape.
From the Figure 4 it can be deduced, that the PES/
MTF yarn has a lower fi eld of elastic deformations (under the yield point) than the 100% PES yarn.
Th e fi eld of viscoelastic region of the PES/MTF yarn is wider and fi nally reaches higher breaking exten- sion (12.6%) than the 100% PES yarn (11.4%).
4 Conclusions
In regard to the research of the infl uence of the fi re resistant modacrylic fi bres in the MAC/CO yarn and the conductive metal fi bres in the PES/MTF yarn on the mechanical and viscoelastic properties in the fi eld of lower loads (5 cN/tex), the following conclusions were drawn:
Th e incorporation of fi re resistant MAC fi bres in
•
the MAC/CO yarn decreases the specifi c break- ing stress level (13.3 cN/tex) – the specifi c break- ing stress of the 100% cotton yarn amounts to 23.0 cN/tex, while the changes of breaking exten- sion are only minor and unimportant. Th e CO fi - bres (5.9%) in the MAC/CO yarn break fi rst (they have lower breaking extension than MAC fi bres – 18.7%) and infl uence the breaking extension lev- el decrease of the MAC/CO (5.8%) yarn in com- parison with the breaking extension of MAC fi bres – 18.7%.
Th e incorporation of conductive MTFs decreases
•
the specifi c breaking stress of the PES/MTF yarn (21.8 cN/tex) – the specifi c breaking stress of the 100% PES yarn is 34.5 cN/tex, while the breaking extension of the PES/MTF yarn is somewhat higher (12.6%).
Th e incorporation of fi re resistant MAC fi bres in
•
the MAC/CO yarn decreases the elasticity modu- lus by about 10% (3.9 cN/tex), which means that the resistance of MAC/CO yarn in the fi eld of lower loads is lower than with the 100% CO yarn (4.3 cN/tex).
On the other hand, the specifi c stress in the yield
•
point of the MAC/CO yarn increases (7.83 cN/
tex) by about 45%, while the specifi c stress in the
yield point of the 100% CO yarn is 5.42 cN/tex, meaning that the fi eld of elastic deformations of the MAC/CO yarn is wider.
Th e incorporation of conductive MTFs decreases
•
the elasticity modulus of the PES/MTF yarn by about 10% (8.6 cN/tex). Th e elasticity modulus of the 100% PES yarn amounts to 9.64 cN/tex.
Th e incorporation of conductive MTFs also de-
•
creases the specifi c stress in the yield point (4.33 cN/
tex) of the PES/MTF yarn, while the specifi c stress in the yield point of the 100% PES yarn amounts to 4.81 cN/tex. Th e region of elastic deformations of the PES/MTF yarn is about 11% narrower.
Based upon the facts presented above, it could be
•
claimed that the incorporation of MAC (mo- dacrylic) fi bres, which are fi re and heat resistant and intended for protective clothing, mostly in- crease the region of elastic deformations as well as the superior elastic properties of the MAC/CO yarn, as was predicted. On the other hand, the in- corporation of MAC fi bres in the yarn decreases the elasticity modulus and increases the deforma- tion level.
Th e incorporation of MTFs (metal-stainless steel
•
fi bres), which are heat resistant and conductive, in the PES/MTF yarn mostly decreases the region of elastic deformations (about 10%). On the oth- er hand, the region of elastic deformations lies very close to the fi eld of lower loads under the specifi c stress/extension curve which amounts to 5 cN/tex or 85 g.
Acknowledgement
Th e authors are grateful to mag. Mirjam Leskovšek for the help in working on scanning electron microscope.
References
1. SCOTT, Richard, A. Textiles for Protection. Edit- ed by R. A. Scott. Cambridge : Woodhead Pub- lishing, 2005, 3–22.
2. HORROCKS, A. R., SUBHASH, C. Anand.
Handbook of Technical Textiles, Edited by A. Ri- chard Horrocks, C. Subhash Anand. 1st Edition.
Cambridge : Woodhead Publishing, 2000, 42–60.
3. LAWRENCE, Carl A. Fundamentals of Spun Yarn Technology. Boca Raton : CRC Press, 2003, 38–44.
4. NDLOVU, Lloyd N., CUNCHAO, Han, CHONG- WEN, Yu. Mechanical and FR properties of dif- ferent ratios of cotton/polysulfonamide (PSA) core spun and blended yarns, Journal of Engi- neered Fibres and Fabrics, 2014, 9(4), 24–33.
5. VALASEVIČIŪTĖ, L., MILAŠIUS, R., BAG- DONIENĖ, R., ABRAITIENĖ, A. Investigation of end-use properties of fabrics from meta aramid yarns. Materials Science, 2003, 9(4), 391–394.
6. LAVRENTEVA, E.P. New-generation fi re- and heat-resistant textile materials for working clothes, Fibre Chemistry, 2013, 45(2), 107–113.
7. OZCAN, Gulay, DAYIOGLU, Habip, CAN- DAN, Cevza. Eff ect of gray fabric properties on fl ame resistance of knitted fabric. Textile Re- search Journal, 2003, 73(10), 883–891, doi:
10.1177/004051750307301006.
8. Textile Innovation Knowledge Platform [dostop- no na daljavo], TIKP [citirano 10. 12. 2014].
Dostopno na svetovnem spletu: <http://www.
tikp.co.uk/>.
9. BUKOŠEK, Vili. Program Dinara® Meritve®. Ljub- ljana : Univerza v Ljubljani, Fakulteta za naravo- slovje in tehnologijo, Oddelek za tekstilstvo, 1989.
10. MISHRA, S. P. A Text Book of Fibre Science and Technology. Edited by S. P. Mishra. 1st Edition.
New Delhi : New age International Publisher, 2010, 363
11. COOK, J. Gordon. Handbook of Textile fi bres:
Man–made fi bres. Reprinted. Cambridge: Wood- head Publishing, 2009, 639–716.
12. BOURBIGOT, Serge, FLAMBARD, Xavier. Heat resistance and fl ammability of high performance fi bres: A review. Fire and Materials, 2002, 26(4–5), 155–168, doi: 10.1002/fam.799.
13. KHAN, Q., Muhammad, SABEEH UL HAS- SAN, Muhammad, HAFEEZ, Sajida. Manufac- turing of industrial fi re retardant gloves using blends of cotton and synthetic fi bres. Edited by Fazul Rehman. International Journal of Engi- neering Sciences & Research Technology, 3(5), 2014, 747–756.
14. VARNAITĖ, Sandra, KATUNSKIS, Jurgis. In- fl uence of Washing on the Electric Charge De- cay of Fabrics with Conductive Yarns. Fibres &
Textiles in Eastern Europe, 2009, 17(5), 69–75.
15. SEKERDEN, Filiz. Eff ect of the constructions of metal fabrics on their electrical resistance. Fi- bres & Textiles in Eastern Europe, 2013, 21(6), 58–63.
16, SABRI OZEN, Mustafa, SANCAK, Erhan, BEY- IT, Ali, USTA, Ismail, AKALIN, Mehmet. Inves- tigation of electromagnetic shielding properties of needle–punched nonwoven fabrics with stainless steel and polyester fi ber. Textile Re- search Journal, 2013, 83(8), 849–858, doi:
10.1177/0040517512461683.
17. SU, Ching–Iuan, CHERN, Jin–Tsair. Eff ect of Stainless Steel–Containing Fabrics on Electro- magnetic Shielding Eff ectiveness. Textile Re- search Journal, 2004, 74(1), 51–54, doi: 10.1177/
004051750407400109.
